Japanese Patent Application Laid-Open Publication No. 2004-96063 (Patent Document 1) describes a technique for providing a phase shift mask of EUV light that can be actually realized by obtaining an appropriate combination of a refractive index and an absorption coefficient even when reflecting the EUV light. More specifically, a phase shift mask is formed by providing a reflective multilayer film substrate which reflects the EUV light and first and second regions formed on the reflective multilayer film substrate. First, with respect to an arbitrary complex refractive index for EUV light and an arbitrary film thickness, a phase and a reflectance of a reflection light of the EUV light obtained from the complex refractive index and the film thickness are specified. Then, based on the specified result, the film thickness and the complex refractive index of each of the film formed in the first region and the film formed in the second region are set so that a predetermined phase difference occurs between the reflection light of the EUV light in the first region and the reflection light of the EUV light in the second region.
In the technique described in Japanese Patent Application Laid-Open Publication No. 2003-315532 (Patent Document 2), the wavelength dependency of reflectance when the EUV light goes through a plurality of reflecting surfaces is controlled to match with the exposure center wavelength of the EUV light, thereby sufficiently ensuring the energy reaching an object to be exposed. More specifically, the reflector of the EUV light used for the exposure to the object to be exposed by the EUV light in the photolithography process for manufacturing a semiconductor device is formed to have a multilayer film structure obtained by repeatedly stacking a plurality of layers in the same order. At this time, the cycle length in units of the repetitive stacking in the multilayer film structure is set so that the half-width center of the reflectance when the EUV light goes through a predetermined number of reflectors and the center wavelength of the EUV light to be reflected are matched.
In the technique described in Japanese Patent Application Laid-Open Publication No. 2006-179553 (Patent Document 3), with respect to an EUV mask in which a first multilayer film to be a high-reflection portion of an exposure light and a first protection film are formed on a substrate, a second multilayer film to be another high-reflection portion and a second protection film are formed thereon, and a pattern made from an intermediate film formed between the first protection film and the second multilayer film is formed, phase difference and intensity of reflection light are precisely determined in accordance with a material of the intermediate film. More specifically, from the characteristics of the reflectance of the first multilayer film and the first protection film and the reflectance of the second multilayer film and the second protection film for the thickness of the intermediate film and the characteristics of the phase difference between the reflection light by the first multilayer film and the first protection film and the reflection light by the second multilayer film and the second protection film for the thickness of the intermediate film, the thickness of the intermediate film is set so that the reflectances are equal to each other and the phase difference becomes 180 degrees.